Gallium nitride (GaN) has various excellent properties such as a bandgap that is about three times as large as that of silicon (Si), a breakdown electric field intensity that is about ten times as high as that of silicon (Si), and further, higher saturation electron velocity than that of silicon (Si). As for GaN, achievement of both high withstand voltage that is difficult in conventional Si power devices and low loss, that is, low on-resistance can be expected, and thus, the application of GaN to a power device (power semiconductor element) such as a Schottky barrier diode (SBD) is expected.
As such Schottky barrier diode, a Schottky barrier diode including a sapphire substrate, a buffer layer formed on this sapphire substrate, an undoped GaN layer formed on this buffer layer, an n-type GaN layer formed on this undoped GaN layer, and a Schottky electrode made of nickel (Ni) or nickel silicide (NiSi) and formed on this n-type GaN layer is disclosed (for example, Non-Patent Document 1). This Non-Patent Document 1 discloses that the barrier height becomes high as a result of heat treatment of the Schottky electrode.